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[Luke Geis]

Ok, so that sums up your current model, but is that for the entirety of all band passes in a system, or just the HF part of that system?

[Ivan Beaver]

Ok, so that sums up your current model, but is that for the entirety of all band passes in a system, or just the HF part of that system?

The lower pass bands can handle the peaks a lot better, plus the power capacity of the lower bands is also high.

But you can run into the same problems running really large amps on full range cabinets.

The HF part of the system is the "weak point" in terms of short term high level signals.

[Don Boomer]

The peak power is 4 times the continuous wattage rating (6dB)-I am suggesting an amp size of only twice continuous.

The peak power comes from the waveform used for power testing.  It has a 6dB crest factor-so a signal that is 100 watts continuous will have 400 watt peaks.

However a test signal is a CONTROLLED situation/  A stage with live mics/instruments-lots of gain on the preamps etc is NOT a controlled situation.

Hence my "argument".

Test conditions are often very different than the real world.

Sorry, i misunderstood you.  You are saying the continuous power of the amp should be no higher than half the peak rated power of the driver.  I though you meant something else.

Like you said, in real world live music situations the dynamic range hopefully is much better than a mere 6dB of dynamic range.  So this suggested amp could very likely be actually delivering double the peak rated power to the driver while still supplying well under the continuous rated power to the driver.

[Ivan Beaver]

Like you said, in real world live music situations the dynamic range hopefully is much better than a mere 6dB of dynamic range.  So this suggested amp could very likely be actually delivering double the peak rated power to the driver while still supplying well under the continuous rated power to the driver.

And this is why I suggest power specs be presented as something like "100 watts continuous OR 400 watts PEAK"

The KEY word is OR!!!!!!!!!!

You DO NOT get both at the same time-despite what people would like.

Let's say you have an that can provide the 400 watt peaks (as per above example).  And you play HIGHLY compressed high freq material so that you are just "tickling" the peak light on the amp.

Let's assume an 8 ohm driver-so this would be 56 Volts

If you were to measure the average voltage going to the amp (with an analog meter) you would see that the voltage would be around 18 volts or less.  This would be around 40 watts or less.

HOWEVER if you had a much larger amp, and were to crank the level so the meter would read around 28V (100 watts @ 8 ohms), the peak levels going to the amp would be around 90 Volts or 1000 watts.

This is a lot above the rating of the driver.

So if you have a large amp-you would be MUCH BETTER off to limit the driver to WELL BELOW its continuous rating.

The limiters will not react fast enough to "grab" the peaks.  So by limiting them much lower, they have a "fighting chance" to help control the peaks.

Once you start looking at how musical signals ACTUALLY respond/behave, you will start to get a new "appreciation" of how to control them.

It is NOT as simple as many would like you to believe.

[Peter Morris]

And this is why I suggest power specs be presented as something like "100 watts continuous OR 400 watts PEAK"

The KEY word is OR!!!!!!!!!!

You DO NOT get both at the same time-despite what people would like.

Let's say you have an that can provide the 400 watt peaks (as per above example).  And you play HIGHLY compressed high freq material so that you are just "tickling" the peak light on the amp.

Let's assume an 8 ohm driver-so this would be 56 Volts

If you were to measure the average voltage going to the amp (with an analog meter) you would see that the voltage would be around 18 volts or less.  This would be around 40 watts or less.

HOWEVER if you had a much larger amp, and were to crank the level so the meter would read around 28V (100 watts @ 8 ohms), the peak levels going to the amp would be around 90 Volts or 1000 watts.

This is a lot above the rating of the driver.

So if you have a large amp-you would be MUCH BETTER off to limit the driver to WELL BELOW its continuous rating.

The limiters will not react fast enough to "grab" the peaks.  So by limiting them much lower, they have a "fighting chance" to help control the peaks.

Once you start looking at how musical signals ACTUALLY respond/behave, you will start to get a new "appreciation" of how to control them.

It is NOT as simple as many would like you to believe.

Hi Ivan,

You just need some better processing  – the Lake LM26 will do everything you need.
http://soundscapesweb.com/files/SAC/Limiters/DLP_LimiterMax.pdf

It just a case of $$$$$

[Ivan Beaver]

Hi Ivan,

You just need some better processing  – the Lake LM26 will do everything you need.
http://soundscapesweb.com/files/SAC/Limiters/DLP_LimiterMax.pdf

It just a case of $$$$$

I might suggest reading the last sentence.

It says
 " As long as the amplifier's power is not over
(under?)
rated for the
loudspeaker,"

So that means (to me) that I am still correct in that you can't use a greatly oversized amp-the whole point of the post.

Or maybe I am reading it wrong.

[Scott Carneval]

It seems to me that the same risk would be present if you were using a high-power amp on a full-range speaker.  For instance, the JBL STX835 is rated 1600/3200/6400 and can be ran full-range or bi-amped.  Let's say you have a 3200 watt amp, and a HF 'pop' is sent down the line.  Well the x-over is going to send all of that energy to the HF diaphragm, right?  The cabinet is rated at 4ohm passive, but the HF is actually 8ohm.  So technically the HF would 'only' see about 1600 watts, but this is still far more than the HF can handle.  Some speakers have passive protection circuits on the HF, but do they react quick enough? And if it works for a full-range speaker, do we need to incorporate them into our bi-amp systems?

Another thought: I typically run all of my amps wide open, and reduce gain in the DSP as necessary.  This prevents someone from inadvertently cranking the gain up on the amp, because it's already all the way up.  If all my amps are sized the same, I might have to pull 10+ db out of the HF in the DSP to get the levels right.  I just attribute this to the (generally) higher sensitivity of the HF vs. the LF.  So if I pull 10db out of the DSP, I'm now sending the HF 1/10th the power of any given signal, correct?  So it seems like this should all 'even out' so to speak.  Meaning that the LF might see a 1000 watt 'pop' but the HF only saw a 100 watt 'pop'.  But I could be missing something.

[Chris Van Duker]

Has anyone ever tried putting a couple of MOVs in parallel with the HF? With proper sizing, you should be able to block those 200V peaks without getting in the way of reasonable transients -- then use the limiter to keep those longer term music transients under control.

[Don Boomer]

And this is why I suggest power specs be presented as something like "100 watts continuous OR 400 watts PEAK"

The KEY word is OR!!!!!!!!!!

You DO NOT get both at the same time-despite what people would like.

I guess it depends on what you consider "at the same time". 

I was curious about the peak to average ratio.  So some years ago I measured the ratio of pink noise with a 6 dB crest factor.  Pink noise is defined as random so you do get numbers all over the place.  But the numbers ranged from about 60 to about 200 peaks per second. so that 100W continuous watt amp would put out 60-200 400w peaks per second while putting out full rated continuous power.  How long this might happen is another story of course.

What does that mean in the real world ... beats me?  I don't go to many pink noise shows   But I am in agreement that using amplifiers that can supply the program rating of the speakers is a good combination of max output from the speakers combined with a reasonable safety margin.  Of course other best practices should be in place as well (HP filtering, limiting and common sense)

[Ivan Beaver]

Has anyone ever tried putting a couple of MOVs in parallel with the HF? With proper sizing, you should be able to block those 200V peaks without getting in the way of reasonable transients -- then use the limiter to keep those longer term music transients under control.

The "problem" with MOVs is that they have a limited life.  Once you hit them X number of times-they simply stop working.

So it would depend on how hard the system is pushed as to how many times they can "absorb" the peaks.  With music-this could be quite a few during 1 show, or not.

Back to back Zeners are another way to keep the peaks down, but they need "something to work against".

But there are limits as to how much the zeners can "handle" in terms of peaks.  THey are more designed for continuous type levels (as in power supplies), but they can help protect if the values are properly chosen.

But just like the air bags in a car-they do not guarantee the "driver" will survive, but they do offer some protection.

[ProSoundWeb Community]